The present invention relates to a sheet post-treating apparatus for treating the sheets which are transferred from an image forming apparatus, more specifically, it relates to a sheet post-treating apparatus in which the sheets transferred from the image forming apparatus are sorted or grouped to the respective sorting trays and then discharged to a discharge tray while a stapling treatment is executed.
In a conventional copying machine or printer, there is a requirement to discharge plural sets of plural pages of copied or printed sheets therefrom. To satisfy this requirement, generally, a sorter is attached to the copying machine or printer. That is to say, by connecting the sorter to the copying machine or printer, the copied or printed sheets are collected onto the respective sorting trays every set in a sorting mode or every page in a grouping mode. As a result, an operator can easily take out the copied or printed sheets from the sorting trays while he or she can distinguish the sheets of each set in the sorting mode or each page in the grouping mode.
Without the post-treating apparatus the sheets must be separately placed on a table stacked by sets or by pages or stacked on the table in a jogged manner to be manually stapled. These post-treatments to the sheets are very troublesome and time-consuming to the operator, especially in a case where there are a large amount of sets or pages.
Conventionally, a sheet post-treating apparatus which was disclosed in U.S. Pat. No. 5,384,634 has been proposed, as shown in FIG. 1. A reference character A in FIG. 1 indicates each of the sorting trays onto which copied or printed sheets P transferred from the copying machine or printer are successively stacked. Each of the sorting trays A is arranged in the sheet post-treating apparatus and inclined to the side surface of a frame D of the sheet post-treating apparatus.
As shown in FIG. 1, a pair of aligning rods B and C for aligning the sheets P in a predetermined position are arranged on both sides of the sorting tray A, respectively. A pair of stapler mechanisms E and F are attached to a portion of the frame D which faces to the rear portion of the sheets P stacked on the sorting tray A. An urging member H for urging the sheets P on the sorting trays A in a discharge direction Y to discharge them to a discharge tray G is arranged on a rear side of the sorting trays A.
The discharge tray G is movable in a discharge direction Y in which the copied or printed sheets P are discharged from the sorting tray A and which is perpendicular to a take-in direction in which the copied or printed sheets P are transferred from the copying machine or printer. The discharge tray G is to be parallel to each of the inclined sorting trays A. That is, the discharge tray G is inclined to the horizontal plane and attached to the front surface of the frame D in such a manner that it meets at right angles to the front surface of the frame D.
In the conventional sheet post-treating apparatus as shown in FIG. 1, a pile of the sheets P stacked on the sorting tray A is collectively discharged therefrom to the discharge tray G in the discharge direction Y by the urging member H while one lateral side of the pile of sheets P is stapled at least one point by the stapler mechanism E and/or F on the way, when a stapling mode is selected.
On the other hand, in the conventional sheet post-treating apparatus, a first pile of the sheets P stacked on the sorting tray A is collectively discharged therefrom to the discharge tray G which is positioned to a first jogging position and a second pile of the sheets P stacked on a next sorting tray A is then collectively discharged therefrom to the discharge tray which is moved to a second jogging position in the discharge direction X, when a jogging mode is selected. Accordingly, the alternate piles of sheets P discharged on the discharge tray G are jogged in the discharge direction Y.
Where the staple mode is selected in the conventional sheet post-treating apparatus, the pile of sheets P is discharged along a flat plane, which is inclined to the horizontal plane, by being pushed by the urging member H in the discharge direction Y.
Accordingly, at first, it is necessary that each of the sorting trays A has a length in the discharge direction Y which length is equal to or longer than that of the sheet P, in the discharge direction Y, because the whole pile of sheets P must be placed on the sorting tray A. If a part of the pile of sheets P is dropped out of the sorting tray A, the outer shape of the pile of the sheets P is bent. As a result, if the pile of the sheets P is stapled by the pair of stapler mechanisms E and F, the bent shape of the pile of the sheets P is fixed. When a two stapling mode is selected for stapling along the same lateral edge, it is usual to simultaneously place both staples. The reason for this is that if the downstream staple is set and the pile P of sheets moved from the upstream edge, there is a tendency for the sheets of the pile to fan up or bulge at the center.
Furthermore, it is necessary that the discharge tray G has a length in the discharge direction Y which length is equal to or longer than that of the sheet P in the discharge direction Y. This means that the discharge tray G must extend to the front side on a large scale, thereby causing the total size of the sheet post-treating apparatus to be excessively large.